Phosphorylation of Arabidopsis response regulator 7 (ARR7) at the putative phospho-accepting site is required for ARR7 to act as a negative regulator of cytokinin signaling |
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Authors: | Dong Ju Lee Sunmi Kim Young-Min Ha Jungmook Kim |
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Institution: | (1) Department of Plant Biotechnology, Agricultural Plant Stress Research Center, Biotechnology Research Institute, Chonnam National University, Buk-Gu, Gwangju, 500-757, South Korea |
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Abstract: | Cytokinins are plant hormones that regulate diverse aspects of plant growth and development. Arabidopsis cytokinin signal transduction utilizes a multi-step two-component signaling (TCS) system by histidyl–aspartidyl phosphorelays.
We here show that phosphorylation of ARR7, an A-type response regulator that acts as a negative regulator of cytokinin signaling,
is required for its function in plants. Phosphorylation of ARR7 is inhibited in vitro by mutation in a putative phospho-accepting
Asp residue into an Asn residue (ARR7D85N). While ectopic expression of ARR7 decreases root-growth inhibition, callus formation, and cytokinin-inducible gene expression, overexpression of ARR7
D85N
at the similar level does not generate these phenotypes. ARR7D85N is localized to the nucleus and the half-life of this mutant protein is similar to that of ARR7 in Arabidopsis mesophyll protoplasts. These results suggest that the phosphorylation of ARR7 is necessary for ARR7-mediated cytokinin response. |
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Keywords: | Arabidopsis Cytokinins Phosphorelay Protoplast Response regulator Two-component |
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